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11.
湿碱消解-等离子体发射光谱法测定海洋沉积物中的生物硅 总被引：2，自引：1，他引：1
利用湿碱式化学提取技术和电感耦合等离子体发射光谱仪,优化样品碱式消解方法,确定仪器最佳工作条件,建立了测定海洋沉积物中不同含量级别生物硅的方法。结果表明,仪器检出限为0.724μmol/L,方法检出限为0.942μmol/L。用于测定硅酸盐-硅溶液成分分析国家一级标准物质(GBW08648和GBW 08649,标准值分别为50.0μmol/L和100.0μmol/L),测定值分别为(49.888±0.275)μmol/L、(99.578±0.651)μmol/L,相对标准偏差为0.443%、0.527%;对于不同生物硅含量级别海洋沉积物样品的平行、独立测量,其相对标准偏差8.9%。方法快速、简便、准确,可满足古海洋学不同时空尺度气候和环境分析的应用。 相似文献
12.
Felipe García-Rodríguez Laura Del Puerto Carola Castieira Hugo Inda Roberto Bracco Peter Spechmann Burkhard Wilhelm Scharf 《Limnologica》2001,31(3)
Physical, chemical and biological data from a sedimentary profile of Rocha lagoon (Uruguay) are presented. Analyses of silica remains showed that opal phytoliths, diatoms, sponge spicules and chrysophyte cysts were the most important contributors to biogenic silica. Organic matter, total nitrogen and total phosphorus were used to infer past trophic development. Physical analysis of sediments allowed us to identify five lithological units related to sea level variation and climatic events. 相似文献
13.
Quaternary biogenic opal records in the South China Sea: Linkages to East Asian monsoon, global ice volume and orbital forcing 总被引：3，自引：0，他引：3
WANG RuJian JIAN ZhiMin XIAO WenShen TIAN Jun LI JianRu CHEN RongHua ZHENG YuLong & CHEN JianFang State Key Laboratory of Marine Geology Tongji University Shanghai China The Key Laboratory of Submarine Geoscience State Oceanic Administration Hangzhou China 《中国科学D辑(英文版)》2007,50(5):710-724
Particulate fluxes investigated in the central South China Sea (SCS) during 1993―1996 indicate that opal flux can be used to show primary productivity change, which provides a foundation for tracing the evolutionary relationship between the surface productivity and East Asian monsoon in the SCS during the late Quaternary glacial and interglacial periods. Based on the studies of opal % and their mass accumulation rates (MAR) at the six sites recovered from the SCS during the “Resolution” ODP Leg 184 and “Sonne” 95 cruise of the Sino-Germany cooperation, opal % and their MARs increased evidently in the northern sites since 470―900 ka, and they enhanced and reduced, respectively, during the glacial and interglacial periods. Whereas they increased obviously in the southern sites since 420―450 ka, and they augmented and declined, respectively, during the interglacial and glacial periods. The vari- ability in opal % and their MARs in the late Quaternary glacial cyclicity indicate the “seesaw” pattern of surface productivity in the SCS. The winter monsoon intensified during the glacial periods, surface productivity increased and decreased, respectively, in the northern and southern SCS. The summer monsoon strengthened during the interglacial periods, surface productivity increased and decreased, respectively, in the southern and northern SCS. The cross spectral analyses between the opal % in the northern and southern SCS during the Quaternary and global ice volume (δ 18O) and orbital forcing (ETP) indicate that the East Asian winter and summer monsoons could be ascribed to the different drive mechanisms. On the orbital time scale, the global ice volume change could be a dominant factor for the winter monsoon intension and temporal variations. As compared with the winter monsoon, the correlative summer solar radiation with the obliquity and precession in the Northern Hemisphere could be a mostly controlling factor for the summer monsoon intension and temporal variations. 相似文献
14.
欧泊的结晶状态和色斑问题一直以来是人们探讨的重要问题.对于区分天然欧泊与人工合成欧泊的重要鉴别特征“丝绢状”和“蜂巢状”色斑的成因问题, 研究甚少.通过宝石学常规测试、扫描电镜、X -射线粉晶衍射等测试手段, 进行测试和分析, 结果表明: 欧泊是由非晶态→雏晶→亚显微隐晶态→隐晶态的这种连续渐变的状态构成, 各状态之间并无截然的界限, 并且可以是这些不同状态的集合体; 提出了欧泊与玉髓之间的宝石学界定标准, 还揭示了两种色斑形成的不同机制: “丝绢”是由天然欧泊内部的显微构造裂隙对光产生散射而形成的, 而“蜂巢”是由合成欧泊自身结构中SiO2球体排布与球体本身透光性决定的.对这两种色斑成因的揭示, 为欧泊鉴定提供了理论依据. 相似文献
15.
Silica stromatolites occur in a number of modern hydrothermal environments, but their formation in caves is very rare. The silica stromatolitic speleothems of the Branca Opala cave (Terceira Island, Azores), however, provide an excellent opportunity for their study. These formations may be analogous to ancient silica stromatolites seen around the world. Petrographic, mineralogical and geochemical analyses were undertaken on the silica speleothems of the above cave, and on the silica‐tufa deposits outside it, with the aim of understanding their genesis. The possible hydrothermal origin of their silica is discussed. X‐ray diffraction analyses showed opal‐A to be the sole silica phase. Negligible ordering of this opal‐A showed ageing to be insignificant, as expected for recent silica deposits. Most of the silica speleothems examined were definable as sub‐aquatic opaline stromatolites that are not currently growing. Optical microscopy clearly revealed a lower microlaminated, an intermediate and an upper microlaminated zone within the stromatolites. Stromatolite types (I, II and III) were classified with respect to their internal structure and distribution throughout the cave. Scanning electron microscopy showed silicified bacterial filaments within the stromatolites, the silicified plant remains and the silica‐tufa deposits. Bacteria therefore played a major role in the precipitation of the opal‐A. Plasma emission/mass spectrometry showed major, minor and rare earth elements to be present in only small quantities. The rare earth elements were mainly hosted within volcanic grains. Rapid silica precipitation from highly super‐saturated water would explain the intense silicification of the plant remains found inside and outside the cave. The opaline stromatolites, the silica‐tufa deposits and the above‐mentioned intense general silicification suggest a local hydrothermal source for the silica. Indeed, these deposits strongly resemble plant‐rich silica sinter associated with low‐temperature hot spring deposits that include bacterial filaments. However, no geochemical signals that might indicate a hydrothermal origin could be found. 相似文献
16.
Lorena Rebolledo Julio Sepúlveda Carina B. Lange Silvio Pantoja Sébastien Bertrand Konrad Hughen Dante Figueroa 《Estuarine, Coastal and Shelf Science》2008
A multi-proxy approach based on organic (organic carbon, alkenones, and C/N) and inorganic geochemical proxies (biogenic opal, inorganic carbon, Fe, Ti, and Ca) preserved in the sediments of the Jacaf channel (CF7-PC33; 44°21′S, 72°58′W, 510 m water depth), Chilean fjords, yields evidence of major past productivity fluctuations in accordance with climatic changes over the last ∼1800 years. The downcore record clearly shows two productivity/climate modes. The first period, prior to 900 cal yr BP, is characterized by decreased marine productivity and a reduced continental signal, pointing to diminished precipitation and runoff. In contrast, the second period between ∼750 cal yr BP and the late 1800s (top of core) is illustrated by elevated productivity and an increased continental signal, suggesting higher precipitation and runoff. Both time intervals are separated by a relatively abrupt transition of ∼150 years which roughly coincides with the beginning of the Little Ice Age. The increased content of freshwater diatoms and Chrysophyte cysts that characterize the last 200 years of the latter mode coincides with a significant decrease in the carbonate content of the sediment; together they further indicate increased terrigenous contributions and decreased marine carbonate productivity at the end of the Little Ice Age. The correspondence between our record and other paleoclimate studies carried out in South America and Antarctica demonstrates that the Chilean fjord area of Northern Patagonia is not just sensitive to local climatic variability but also to regional and possibly global variability. 相似文献
17.
Sunghan Kim Kozo Takahashi Boo-Keun Khim Yoshihiro Kanematsu Hirofumi Asahi Ana Christina Ravelo 《Quaternary Research》2014
Biogenic opal content and mass accumulation rate (MAR) at IODP Expedition 323 Site U1343 were found to fluctuate consistently, generally being high under warm conditions and low under cold conditions during the last 2.4 Ma. Continuous wavelet transform analysis of the normalized biogenic opal content indicates that export production in the Bering Sea varied predominantly at 41-ka periodicity before 1.25 Ma, and shifted to 100-ka periodicity at the onset of the Mid-Pleistocene Transition (MPT; 1.25–0.7 Ma). The 100-ka cycles dominated until the Holocene. Export production in the Bering Sea decreased markedly in the Bering Sea two times during the MPT: the first occurred at the beginning of the MPT (1.25 Ma) and the second in the middle of the MPT (0.9 Ma). These decreases coincided with both increases in the relative abundance of sea-ice diatoms and decreases in the warm-water diatom species Neodenticula seminae, indicating that reductions in export production in the Bering Sea during the MPT were associated with climate cooling. Decreases in export production in the Bering Sea during the MPT were most likely associated with the increased influence of polar/Arctic domains on the high-latitude North Pacific. 相似文献
18.
应用XRF-SEM-XRD-FTIR等分析测试技术研究丽水蓝色类欧泊(蛋白石)的矿物学与光学特征 总被引：2，自引：2，他引：0
直至目前,我国相关欧泊的矿藏及其相应的矿物学特征鲜见报道,近期在浙江丽水缙云地区发现的蓝色类欧泊石引起了宝玉石科研工作者的广泛关注,但此矿物的相关研究至今尚未见论述。本文应用X射线荧光光谱(XRF)、场发射扫描电镜(FE-SEM)结合X射线粉晶衍射(XRD)与傅里叶变换红外光谱(FTIR)等多种综合检测技术首次对该类蓝色原矿的矿物学及光学变彩性质进行研究。结果表明:XRF分析显示蓝色原矿的主体化学组成为SiO2(质量含量95%),仅含极少量的Fe2O3与Al2O3等杂质。同时,蓝色原矿及其相应的热处理后样品局部区域具有明显的变彩特征,主体的化学组成与其光学特征与天然欧泊的组成及变彩效应类同。XRD分析显示原矿粉体的无机相的晶型为方石英相,衍射峰形锐化,该晶体的结构特征明显相异于天然欧泊即微晶类的蛋白石(Opal-CT)、Opal-C与非晶蛋白石类(Opal-A)。此外,样品的红外光谱与天然欧泊间存在一定的频率位移。鉴于此,初步将该类原矿归属为类欧泊,因蓝色原矿所在地丽水缙云地区属于中生代陆相火山岩的地质,因此进一步将该原矿命名为一类火山岩类的类欧泊石,而有关此类欧泊是否可以归属为广义上的欧泊有待再作商榷。同时基于对蓝色原矿有无变彩效应区域的FE-SEM测试结论,本文初步推测该类矿物的光学变彩特征与原矿表面的“叠瓦状”结构形貌有关。 相似文献
19.
目前,埃塞俄比亚染色欧泊在我国市场上屡见不鲜.本文采用常规宝石学测试手段、光谱分析、吸水实验、浸泡褪色实验和浸泡染色实验等方法对市场上常见的3种颜色的埃塞俄比亚染色欧泊进行了研究.结果表明,这些埃塞俄比亚染色欧泊主要通过浸泡于不同颜色的化学颜料溶液中上色,浸泡过程中往往添加含有羧酸根离子的表面活性剂或颜料超分散剂(如邻苯二甲酸酯),以使颜料颗粒分布更加均匀,这主要是由于埃塞俄比亚欧泊的孔隙度相对较大,对染料的吸附性相对较强.这些埃塞俄比亚染色欧泊的主要特征如下: ① 亚透明至微透明,染橙色和染蓝色样品具有弱至强的变彩,染黑色样品体色以灰蓝色或黄灰色为主,具有强烈的红色、黄色、绿色和蓝色变彩;透射光下照射,染黑色欧泊具有强至弱的红色调以及明显的染剂不均匀富集现象. ② 埃塞俄比亚染色欧泊和其天然欧泊一样吸水性强,吸水后密度、质量均有所增加,透明度增强,变彩可能会有所增强,也可能会有所减弱,染色欧泊密度范围为1.63～1.86 g/cm3,折射率在1.40(点测)左右,与天然欧泊一致,均低于澳大利亚和墨西哥的欧泊. ③ 在高倍显微镜下观察,染色样品颜色分布不均,内部常见色点、色斑、色块或色团分布,在表面部位染剂富集现象更为明显,常见染剂沿着边缘、刮痕或凹坑处富集. ④ 染色欧泊浸泡在不同的溶剂中会使溶剂变色. ⑤ 拉曼光谱表明,染色欧泊出现了很强的荧光背景及弱的热效应峰3 362 cm-1,拉曼散射峰很弱. ⑥ 紫外可见光分光光谱表明,埃塞俄比亚染色欧泊与天然欧泊的吸收光谱不同. 相似文献
20.
Elsa Arellano-Torres Astrid J. Mora-Rivera Paola Vázquez-Romero Enrique H. Nava-Sánchez Juan José Kasper-Zubillaga M. Socorro Lozano-García 《第四纪科学杂志》2020,35(3):479-491
We study the marine and terrestrial contributions in the Gulf of California (GC) to understand the relationship between continental climate and oceanographic variability over the last 28 ka. In Core AII125-8-JPC-20, we examine aeolian and riverine inputs as nutrients for biological productivity. We use biogenic silica (%opal), total organic carbon (%TOC) and calcium carbonate (%CaCO3) as proxies for primary productivity, and lithic fraction distributions as proxies for terrigenous transport. At the core site, biogenic and lithic components are in phase at millennial-scale in response to regional climate conditions. During the Late Pleistocene, the GC shelf area was above sea level and the western margin showed transient episodes of increased fluvial inputs. Episodic increases in %opal and reduced %TOC suggest upwelling events but ineffective C-export to the sediment. During stadial events (Heinrich 2, Heinrich 1, Younger Dryas), regional declines in %opal, but increases in %CaCO3 and TOC, suggest efficient C-export by carbonate organisms. During most of the Holocene, dust inputs are higher. Episodic increases in %TOC suggest higher C-accumulation, although this is not controlled by siliceous or calcareous organisms. In the GC, besides upwelling and current advection, nutrient inputs driven by terrestrial climate have an impact on the biological C-pump. © 2020 John Wiley & Sons, Ltd. 相似文献